At this moment I would regard this as a partial answer or better a draft (I'd even recommend anybody to not vote for it by now, but feel free to comment).
Please note that I don't know this sheikh nor the content of the lecture he has given about LGBT rights. But be aware that such people as long as they don't follow their desires and act upon them in public have the right of being respected in Islam, as they are humans as all of us. For these kinds of people the final judgment is up to Allah and none can pretend that those among them claiming to be Muslims or believers are not. Whom of us knows about Allah's recompense for people who fought their desires for a life time and kept away from haram?.
So basically defending these rights is not something against Islam. It would be against Islam if one would say that homosexual acts are acceptable, this could be regarded at least a as bid'ah(innovation):
The best discourse is God’s Book, the best guidance is that given by Muhammad, and the worst things are those which are novelties. Every innovation is error.” (Mishkat al-Masabih)
Messenger of Allah (ﷺ) said, "If anyone introduces in our matter something which does not belong to it, will be rejected".
A hadith about types of people (scholars) in their benefit for themselves and others
There's a Sahih hadith with the following wording:
Abu Musa reported Allah's Apostle (ﷺ) as saying:
The similitude of that guidance and knowledge with which Allah, the Exalted and Glorious, has sent me is that of rain falling upon the earth. There is a good piece of land which receives the rainfall (eagerly) and as a result of it there is grown in it herbage and grass abundantly. Then there is a land hard and barren which retains water and the people derive benefit from it and they drink it and make the animals drink. Then there is another land which is barren. Neither water is retained in it, nor is the grass grown in it. And that is the similitude of the first one who develops the understanding of the religion of Allah and it becomes a source of benefit to him with which Allah sent me. (The second one is that) who acquires the knowledge of religion and imparts it to others. (Then the other type is) one who does not pay attention to (the revealed knowledge) and thus does not accept guidance of Allah with which I have been sent.
(Sahih Muslim and also in Sahih al-Bukhari with a small difference in the wording)
This hadith shows three categories of people in their studying, understanding and preaching or teaching knowledge.
- People who have a good ability to learn and teach and who practice what they say: they are guided and guide others.
- People who have a good ability to learn and teach (one could say they rather have a good memory), but hardly practice what they say: one may say they are hardly guided, but can guide others.
- People who neither are guided nor could guide others, as they don't care about knowledge.
This hadith leaves the impression that one could certainly profit from the knowledge of the two first categories of people. But as for the second one must have the ability to preselect or pic what one needs or what is useful and leave aside what isn't.
From the commentary on the hadith
Imam an-Nawawi summarizes the meaning of the hadith in his commentary on Sahih Muslim -see here in Arabic- as follows:
In the following I'm translating from Arabic language, as these interpretations are of my own take them with the necessary care!
أما معاني الحديث ومقصوده فهو تمثيل الهدى الذي جاء به صلى الله عليه وسلم بالغيث ، ومعناه أن الأرض ثلاثة أنواع ، وكذلك الناس .
As for the meanings and intent of the hadith, it is the representation of the guidance that the prophet Allah's peace and blessings be upon him brought as the example of rain, and it means that the earth is of three types, and so are people.
فالنوع الأول من الأرض ينتفع بالمطر فيحيى بعد أن كان ميتا ، وينبت الكلأ ، فتنتفع بها الناس والدواب والزرع وغيرها ، وكذا النوع الأول من الناس ، يبلغه الهدى والعلم فيحفظه فيحيا قلبه ، ويعمل به ، ويعلمه غيره ، فينتفع وينفع .
The first type of land benefits from rain, so it lives after it was dead, and pastures grow, so people, animals, crops, etc. benefit from it, as well as the first type of people, who is informed by guidance and knowledge, so he preserves it, so his heart lives, works with it, teaches others, and he benefits and others benefit from him.
والنوع الثاني من الأرض ما لا تقبل الانتفاع في نفسها ، لكن فيها فائدة ، وهي إمساك الماء لغيرها ، فينتفع بها الناس والدواب ، وكذا النوع الثاني من الناس ، لهم قلوب حافظة ، لكن ليست لهم أفهام ثاقبة ، ولا رسوخ لهم في العقل يستنبطون به المعاني والأحكام ، وليس عندهم اجتهاد في الطاعة والعمل به ، فهم يحفظونه حتى يأتي طالب محتاج متعطش لما عندهم من العلم ، أهل للنفع والانتفاع ، فيأخذه منهم ، فينتفع به ، فهؤلاء نفعوا بما بلغهم .
The second type of land is one that does not accept use in itself, but it has a benefit, which is the holding of water for others, so that people and animals benefit from it, as well as the second type of people, they have hearts that protect, but they do not have perceptive understandings, and they do not have a firmness in the mind in which they derive meanings and judgments. And they do not have a diligence in obedience and act upon it, for they preserve it until a needy student who is thirsty for their knowledge comes and is qualified for benefit and from whom others may benefit too, and he takes it from them, and he benefits from it, these kind of people have made others benefit from what they've reached.
والنوع الثالث من الأرض السباخ التي لا تنبت ونحوها ، فهي لا تنتفع بالماء ، ولا تمسكه لينتفع بها غيرها ، وكذا النوع الثالث من الناس ، ليست لهم قلوب حافظة ، ولا أفهام واعية ، فإذا سمعوا العلم لا ينتفعون به ، ولا يحفظونه لنفع غيرهم . والله أعلم .
And the third type is swollen land that does not sprout or alike, for it does not benefit from the water, nor does it hold it so that others can benefit from it, and likewise the third type of people, they do not have hearts that keep them, and they do not have conscious understanding. God knows .
وفي هذا الحديث أنواع من العلم منها ضرب الأمثال ، ومنها فضل العلم والتعليم ، وشدة الحث عليهما ، وذم الإعراض عن العلم . والله أعلم .
This hadith is about proverbs and examples, the virtue of knowledge and education, the intensity of their urging, and the denunciation of turning away from knowledge. And Allah knows best.